Attachment of integrated circuit packages, such as ball grid arrays (“BGAs”), to circuit boards may require careful thermal considerations. For example, attachment of a tile-based transmit/receive (“TR”) module for a phased array radar to a circuit board with a BGA approach requires that the thermal interface not interfere with the ball attachment. The thermal interface should be of sufficient flexibility so that it does not cause a separation between the TR module and the circuit board by placing sufficient stress on the solder balls.
Merely having an air interface is not sufficient because the low thermal conductivity of air is not sufficient for heat transfer. Placing solid materials between the integrated circuit packages and circuit boards could meet thermal conductivity requirements, but it would be impractical because of the tolerances involved. Compliant materials placed in the gap would possible mitigate thermal stress concerns on the solder balls, but compliant materials with high thermal conductivity are not available.